In the Edit Post page how do I modify with jQuery the status select list?

Your first line works for me when I type it in the console of Chrome:

jQuery('#post_status option[value="draft"]').text('Approve');

so I assume your problem may be that the element you want might not be loaded yet from where you run your script. Try wrapping it in this:

jQuery(document).ready(function() { 
    (function ($) { 

        $('#post_status option[value="draft"]').text('Approve');

    })(jQuery);
});